Figure 2. PIP₂ binding site.

a, A detailed view of the PIP₂ binding site is shown in the same orientation as outlined in figure 1c. Helices (shown as ribbon) from different subunits are colored orange and cyan interior. Residues hydrogen bonded (dashed lines) to PIP₂ are colored green, and residues stabilizing the PIP₂ binding site in the CTD while lacking direct contact are colored blue. All side chains are shown as sticks. PIP₂ is shown as sticks and colored according to atom type: carbon, yellow; phosphorous, orange; and oxygen, red. b, An amino acid sequence alignment of selected eukaryotic Kirs showing residues predicted from literature (blue outline) and not predicted (purple outline) to interact with PIP₂9,28. Residues with direct bonding interactions to PIP₂ and with a structural role are highlighted with green and blue shade, respectively. The two residues serving as the inner helix gate are also highlighted with grey shade.